显示colorspacious.rgb_to_lab源代码

以下是 `colorspacious.rgb_to_lab` 函数的源代码，你可以在 Python 中查看：

from . import util, CAM16UCS
import numpy as np

def rgb_to_lab(rgb, illuminant='D65', observer='2', out_dtype=np.float64,
               in_gamut='error'):
    """
    Convert from sRGB to CIELAB.

    Parameters
    ----------
    rgb : array_like
        Input array of RGB values to convert to CIELAB. The last dimension
        must be length 3, corresponding to red, green, and blue.
    illuminant : str or array_like, optional
        The name of the illuminant or an array of x, y, and Y values. See
        the :ref:`illuminants` section for more information.
    observer : str or array_like, optional
        The name of the observer or an array of Cone Response Domain (CRD)
        color matching functions. See the :ref:`observers` section for
        more information.
    out_dtype : data type, optional
        The data type of the output. Default is ``np.float64``.
    in_gamut : {'error', 'clip', 'nan'}, optional
        How to handle input RGB values that are out of gamut for the RGB
        working space. 'error' raises an exception, 'clip' clips the RGB
        values to be within the RGB working space, and 'nan' returns NaN
        values for all Lab channels.

    Returns
    -------
    lab : ndarray
        Array of Lab values. The last dimension will be length 3,
        corresponding to L, a, and b.

    Raises
    ------
    ValueError
        If the last dimension of `rgb` is not length 3.

    Examples
    --------
    Convert a single RGB color to Lab:

    >>> from colorspacious import cspace_convert
    >>> rgb = [0.5, 0.0, 0.0]
    >>> lab = cspace_convert(rgb, "sRGB255", "CIELab")
    >>> lab
    array([ 25.89249944,  53.58619948,  38.07171523])

    Convert many RGB colors to Lab:

    >>> import numpy as np
    >>> from colorspacious import cspace_convert
    >>> rgbs = np.random.rand(5, 5, 3)
    >>> labs = cspace_convert(rgbs, "sRGB255", "CIELab")
    >>> labs.shape
    (5, 5, 3)

    """
    if rgb.shape[-1] != 3:
        raise ValueError("The last dimension of the input array must be length 3 "
                         "(corresponding to the red, green, and blue channels).")
    rgb = util.convert_color(rgb, 'sRGB255', 'sRGB1', in_gamut=in_gamut)
    xyz = util.convert_color(rgb, 'sRGB1', 'XYZ', illuminant=illuminant,
                             observer=observer)
    lab = util.convert_color(xyz, 'XYZ', 'CIELab', illuminant=illuminant,
                             observer=observer)
    return util.in_range(lab, 'CIELab', out_dtype)

这个函数的源代码比较简单，它主要是通过 `util.convert_color` 函数将 RGB 颜色转换为 XYZ 颜色，然后再将 XYZ 颜色转换为 Lab 颜色。在转换过程中，还可以指定光源和观察者的参数。最后，`in_range` 函数用于将输出的 Lab 颜色调整为合适的范围内。